The present invention is a phase change material more particularly, the present invention is a phase change material for maintaining a food product in a frozen state.
During the distribution of frozen food products, such as ice cream, it is essential to maintain the food products at a sufficiently low temperature so that the food products remain frozen prior to consumption. For example, home delivery services have been developed to deliver various food products to a consumer's home and thereby eliminate the need for the consumer to go to a store to purchase the food products.
It is not always possible to store food products in a mechanically cooled freezer compartment during the distribution of the frozen food product. This is particularly true with home delivered frozen food products where it is not always possible for the consumer to be at home when the frozen food products are delivered.
For these types of situations, the delivery company typically provides an insulated container at the consumer's home. The insulated container holds the frozen food products until the consumer arrives back at home and is able to put the frozen food products in a mechanically cooled freezer compartment within the consumer's home.
It is frequently necessary to place cooling aids in the insulated container to maintain the frozen food products at a sufficiently low temperature so that the food products remain frozen until the food products are removed from the insulated container. Because these cooling aids are ancillary to the purchase of the frozen food products, it is desirable to make the cooling aids as inexpensively as possible. Examples of cooling aids are ice, dry ice, and coolant pouches.
To ensure that the food products remain frozen until removed from the container, it is desirable for the cooling aids to be frozen to a temperature that is at least 5.degree. F. less than the melting temperature of the frozen food products. At the same time, it is desirable to use a cooling aid where the frozen temperature of the cooling aid is not substantially below the frozen food product because of the cost associated with purchasing the cooling aid becomes progressively larger as lower temperatures are used. Additionally, using a cooling aid that has a temperature significantly below the frozen food product increases the likelihood that the cooling aid will cause freezer bum on the frozen food product.
It is also desirable for the cooling aids to have a melting temperature that is at least 5.degree. F. less than the temperature of the frozen food product. If the cooling aid has a melting temperature that is within this range, a maximum amount of energy is extracted from the cooling aid.
While ice is plentiful and relatively inexpensive to produce, the is melting temperature of ice is greater than the melting temperature of many frozen food products. As such, ice is not a desirable choice for maintaining foods products at a sufficiently low temperature that the food products remain frozen.
Dry ice has a substantially lower melting temperature than most food products. However, the extremely low temperature of dry ice makes it likely that the dry ice will produce freezer burn on the food products. Additionally, the extremely low temperature of dry ice makes handling dry ice hazardous and it is not possible to reuse dry ice.
Prior art coolant pouches containing phase change materials while being reusable have melting temperatures that are not at least 5.degree. F. lower than the melting point of the food products. As a result, the prior art coolant pouches are not very effective at maintaining the food products in a frozen state.
Cooling aids with these properties are commonly referred to as phase change materials because they are designed to change phase from a solid to a liquid while the cooling aid is used. It is also desirable for the cooling aid to be easily formulated from food-grade ingredients and readily change phases without the use of nucleating agents.